Minimal Detection of Nuclear Mutations in XP‐V and Normal Cells Treated with Oxidative Stress Inducing Agents

Abstract

Elevated levels of reactive oxygen species (ROS) can be induced by exposure to various chemicals and radiation. One type of damage in DNA produced by ROS is modification of guanine to 7,8-dihydro-8-oxoguanine (8-oxoG). This particular alteration to the chemistry of the base can inhibit the replication fork and has been linked to mutagenesis, cancer and aging. In vitro studies have shown that the translesion synthesis polymerase, DNA polymerase η (pol η), is able to efficiently bypass 8-oxoG in DNA. In this study we wanted to investigate the mutagenic effects of oxidative stress, and in particular 8-oxoG, in the presence and absence of pol η. We quantified levels of oxidative stress, 8-oxoG levels in DNA, and nuclear mutation rates. We found that most of the 8-oxoG detected were localized to the mitochondrial DNA, opposed to the nuclear DNA. We also saw a corresponding lack of mutations in a nuclear encoded gene. This suggests that oxidative stress’ primary mutagenic effects are not predominantly on genomic DNA.

Deletion of the GAPDH gene contributes to genome stability in Saccharomyces cerevisiae

“…DNA damage caused by ROS appears as an oxidized base, a sugar modification, a DNA or protein crosslink or a DNA strand break [47][48][49] . 8-Oxoguanine, a representative oxidized DNA adduct, works as a replication fork blocker 50,51 . The accumulation of DNA damage causes replication fork stalling, which provides an opportunity for HR between direct repeats on the DNA strand.…”